is the working tree dirty?

gistfile1.txt

# This is the function that git-rebase--interactive uses to determine if the
# working tree is clean, and to bail out if not
require_clean_work_tree () {
        # test if working tree is dirty
        git rev-parse --verify HEAD > /dev/null &&
        git update-index --ignore-submodules --refresh &&
        git diff-files --quiet --ignore-submodules &&
        git diff-index --cached --quiet HEAD --ignore-submodules -- ||
        die "Working tree is dirty"
}